#include <iostream>
#include <cstdio>
#include <string>
#include <vector>
#define NMAX 100005
#define MMAX 500005

using namespace std;

int n, m;
int mlc;

vector<int> vec[NMAX];

bool grad()
{
    for (int i=1; i<=n; i++)
        if (vec[i].size() % 2 == 0)
            return true;
    return false;
}

vector<int>::iterator it;

void stergere(int x, int y)
{
    for (it = vec[x].begin(); it != vec[x].end(); it++)
    {
        if (*it == y)
        {
            vec[x].erase(it);
            break;
        }
    }
}

void euler(int k)
{
   while(!vec[k].empty())
   {
       mlc = vec[k].back();
       vec[k].pop_back();
       stergere(k, mlc);
       euler(mlc);
   }

   printf("%d ", k);
}

void read()
{
    scanf("%d %d\n", &n, &m);
    int x, y;
    for (int i=1; i<=m; i++)
    {
        scanf("%d %d\n", &x, &y);
        vec[x].push_back(y);
        vec[y].push_back(x);
    }
}

void solve()
{
    if (!grad())
        printf("-1");
    else
        euler(1);
}
int main()
{
    freopen("ciclueuler.in", "r", stdin);
    freopen("ciclueuler.out", "w", stdout);
    read();
    solve();
    return 0;
}